Shock absorber



Dec-m. 2, 1947. I E, F, ROSSMAN 2,431,966

SHQGK ABSORBER Filed Aug. 26, 1946 Patented Dec. 2, 1947 -'GeneralMotors Corporation, DetroitQAMich.; a.

corporation of Delaware UNITED STATES PATENT OFFICE.

Applicationaugstzs, lais-,lserial No. aes-,03o

* 11 Claims.

This invention relatesftoimprovements inrhydraul'ic shock absorbersand"particularly-tow the type known as directv acting shockrabsorbers.

'Itisfamong the objects ofthewpresent invention to provide a directacting hydraulicshock absorber WithV both pressure actuatedAand-.inertia Weight controlled -fluid llovv control devices whichrespectively'regulate tlieaction of Ythe shock abe sorber in accordanceWith'fluid. pressures built up Within the shock absorberendl theaccelerations and'vdecelerations inthe movements ofthe uiddisplacement-memberof the shockabsorber.

Another object ofthe present. invention is to` provide a directactingmydraulicshock absorber in which all controlling uid Iiows aredirected through theuiddisplacementmemberonly.

vFurtherv objectsand advantages of the 4present invention Willibeapparent from the. following description, reference being'had to theaccompanyingfdrawings, wherein fa preferred embodimentofthe presentinventionis clearly shown.

In the drawings:

Fig. 1 isV a longitudinalfsectional-View ofthe shock. absorber equippedWith the present invention.

Fig. 2 is a fragmentary. sectional View of the valve cage andhitscontained valves. the, valves being shown in aposition. differentfromthat of Fig.l l;

Fig. 3 is a transverse sectiontakenalong the line 3-3-o'f Fig. `1.-

Fig. 4 is a'fragmentary sectional Viewy at en. larged scale. showinglthe. details of construction ofone of the fluid flowcontrol valves.

The present directacting, hydraulic shockabsorber comprises l aplurality.. of concentricallyarranged tubular members, the innerorsmallest diameter tube forming Vthe .Workingscylinderl Ahead membern2| Vhas a pluralityof.concentric, annular4 portions',v the smallestdiameter portion 22--extending into-and press-ttedvl-into theY one endofthe cylinder 20. The secondftube/ZS, surrounding t'hec'ylinder .20,so-as to .form .aspace 2:1 4between tubes 2l] Aand.23, ispress-tted-,uponthe annular portion 2530i the khead membem At various ponts'in thesurfaeeof theannular por tion 25, shallow notches orgrooves.26..areformed therein'for providing aiescapement ducts. The third`tubular.member 2l surrounds tube 23 ,for aportion of its lengthsandisof .such adiamter as to provide anarrowannularspace 28^between itvandtubei 23. The onefendpitube 21 isared outwardly to seat upon. a. conical.orlslopingfsurface of theuhead.memberfaeainst which itis clamped `aswill be described.. The next, or 4fourth (c1. leef-ssl 2 tube 30jVsurroundswtubes 231x and 21 andforms the' annular reservoir space 3 Ibetweenitand tube 23;. 'Ijhe one end oftube 3|) is interiorly'` threadedV'to receive )the threaded, largest diame-v ter portionofthenheadfmember 2|. A vcollar 32 resting, chuanA annular shoulder(inside tube 3D, engages andjpresses aresilient packing gasket upon theYaredend'of tube] and thusvholds Seidiiube in position, uponsaid headvmember When it,` the headmernben issCreWed into tube 39;- Theotherend'of tube ,30j is `closed'in any suitable manner, ,the presentdrawings Vshowing a cup-shaped portion 3d-being Welded thereto. On theinside of-cup3 4;ribs 35are4provided upon which certain partsof'theshockabsorber rest while` still providing liluid passages.

The head-'memberuZsI-has a central opening l 3'| which is recessed-asat'38` to providealargelj diameter openinginftheouter surfacerof thehead member. A? packing gland'- 33; of any suitable designor-constructiomuis seated and secured in recess 38j.` Portion 4Uof thepiston rod,A desig-y natedas a Wholeby the numeral 4I, slidablyex'-tends throughr the `*packing* gland; 34- and the opening 3120i theheadmember into the cylinder 29.;` :The end of the piston rod :portion40, extendingninto the cylinder, is centrally recessed and interiorthreads are provided in this recess adjacent rits inner end, the outerend being smooth. A disc- 42' is attached to piston rod portion 40outside the packinggland 39 `and to the annular', peripheral surfaceofsaid disc, *one end oitube 43-isl secured. This tube surrounds tubeEiland iscomparatively shorter, forming aV guard and dustpshieldaround'the top portion ofthe shock absorber. When in fullycollapsedposition-as shown,Y the disc -rests upon the head mem ber 2|and `end of tube 3|lsecured thereto.

An. intermediate-recess in the bottomkvof the recess 38 -of head member2| forms a space 44 Which is in communication with the annular spaceK28e-between the-tube 23 -and the baille tube 21- by ducts 45providedlin'the headmember 2|. 'I 'hisprovidesfor the returnof fluid tothe .reservoir 3| `whichmayY leak -past the bearing surfaces betweenpiston rod portion 40- and the'openingll in thehead member.

Theb-ottom. or end -of thevcylinder -20 lopposite then headsmem-ber.` 2|is `provided witha valve cage 5|),a cylindrical extension 5| ispress-fitted intothisend Ot-thecylinder. The lower endxof tube V23 ispress-fitted uponr--a larger diameter annular V.portion of -said yvalvecage.' A central openingf52 .inthe valveage provides abearng in which alsleeve valvellbalanced so -as -tobe non-operative by fluid pressure, isslidably supported. When the shock absorber is assembled, cage 59 restsupon the ribs 35. Valve cage 55 has radial openings 53 in its annular,peripheral wall which openings are in constant communication with th-espace 24 between the tubes 25 and 23. This space is also incommunication with the inside of the cylinder tube 25 through openings55 in said cylinder tube, said openings being adjacent the surface ofthe head member inside the cylinder 2t. A plurality of grooves in thevalve cage lead from the openings 53 to the annular surface of a centralopening 52 in the valve cage. An annularrgroove 55 in the outer,peripheral surface of the sleeve valve forms an annular chamber in thecage 5i) which is in communication with the grooves 55 at all times. Theone end of sleeve-valve 55 is flared out as at 5| providing an annularledge which is yieldably urged into seating engagement with the outer,annular edge of opening 52 in the Valve cage by a series of springlingers |32 provided in the ring 63, the peripheral portion of which isattached to the valve cage in any suitable manner, Sleeve valve 55 isbalanced so as to be unaffected by fluid pressure acting on the annularwall of its groove which forms chamber 55.

The valve cage 5e also contains a fluid replenishing or intake valve Y@which normally shuts oif communication between the interior of cy in der20 and the fluid reservoir 5I but under certain circumstances isactuated to permit a uid flow from the reservoir into the cylinder. Thisvalve i il comprises two ring shaped, resilient discs, the centralopenings in which fit over a hub 'H formed on the carrier cisc l2 andsecured to sail disc 'l2 in any suitable manner, preferably by swagingor spinnin I a portion of said hub over the outer valve disc. At itsouter edge, carrier disc 12 is provided with a plurality of slots o-rcut-away portions i3 so thatY the peripheral edge of said disc liesclosely to the inner annular wall of the extension 5| of the valve cagefor guiding purposes while the slots 'i3 permit uid flow past the discl2. The outer annular edge of the outer disc of valve TU is normallyyieldab-ly held in engagement with the armular ledge l@ surrounding theopening 52 inthe valve cage by spring ngers l5 provided by the ring l5which is secured in the valve cage by swaging portion 'il of the valvecage over ring 5.

As shown in Fig, l, the end of sleeve valve 65 adjacent ledge or seat 'Min the valve cage has an annular ridge forming a seat Eid which isnormally heldin close proximity to Valve i0 by the action of springfingers 52. However, when fluid pressure upon disc 'i2 urges itdownwardly from its normal position as shown in` Fig. l into theposition as shown in Fig. 2, then flexing of spring disc valve le due tosuch fluid pressure causes it to engage the seat 6 l, thus valve ilmechanically moves the sleeve-valve 66 from engagement with the outerannular edge of the valve cage surrounding opening 52 and thus openscommunication between annular space 24 and the fluid reservoir.

The piston rod i l, as has been stated, comprises a portion di! whichslidably extends through opening S7 in the head member 2| into theinterior of the cylinder 29. Also that the inner end of piston rodportion di) is recessed, the inner end of the recess being interiorlythreaded, the outer end smooth. This threaded recess in portion @ilreceives the threaded end of the oher tubular piston ro-d portion |52,the outer end of which has an outwardly extending annular flange forminga head M3. This tubular piston rod portion H32 has three annular groovesformed in its outer periphery. The first groove lei-l is adjacent thethreaded end of this piston rod portion and has a series of openingsUlli in portion |22 communicating therewith, Similar openings |55 in therod portion 49 also communicate with said groove hit, The second orintermediate groove its has openings lill in the portion |42communicating therewith. rlhe third or lowermost groove |58 is incommunication with openings li in piston rod portion |42. Betweenopenings me and head |53, the piston rod portion |42 has another seriesof radial openings |58.

A plurality of elements making up the fluid displacement member and itscontrol elements are mounted on the piston rod portion |532 and theywill be mentioned in their order from top to bottom. First a ring block|5| fits about piston rod portion H22 and abuts against the end ofpiston rod portion liti. A cylindrical extension projects om the bottomofblock |5l, the end of said extension being notched as at |52. Acentrally apertured disc spring |53 engages the outer end or thecylindrical extension on block |5|, the notches providing for iiuid flowthrough the extension on the block. Next a spacer collar l5@ engagestlie spring |53 and trie spacer co1 ar in turn rests upon a resilientring-disc valve |55 which rests upon the upper surface of the pistonblock One or more centrally apertured disc springs |57 surround thespacer collar |55 and are held spaced from the disc valve |55 by aspacer collar 55d whose inwardly extending liange is between the valve|55 and the adjacent disc spring i5?. As will be described springs |57are used to load the disc valve |55, Fig. 4 clearly shows theconstruction of this valve mechanism which is identical with the valvemechanism at the opposite end of the piston |55. The bottom end surfaceof the piston is engaged by a resilient discspring E58 which, like discspring |55, may be supplemented by a series of additional spring discs59. rhese discs |53 surround a spacer collar |55 engaging the disc valve|58 and in turn engaged at its bottom end by a ring shaped spring |6|which rests upon the notched end of an annular extension on ring block|52. The bottom surface of blo-ck |62 is radially channelled orcorrugated and is engaged by the end Wall of a container |54. A bumperspring |65 is clamped against the inner end wall of the container |64.Thus it will be seen that as the piston rod portion E42 is screwed intothe portion all these elements |5| to |85 inclusive will be held inclamped assembly on the piston rod.

A cup-'shaped piston |70 has an opening in its bottom slidably fittingabout the spacer collar |54, the cylindrical portion of said membertting slidably about the block |5l. As has been stated heretofore,spring |53 has its inner annular portion clamped between the block |5|and the spacer collar 54. Its outer annular portion engages and restsupon the inner surface of the cup-shaped piston I'I so as to bepredeterminately flexed thereby exerting a force upon the piston i tourge its extension upon the upper spring disc 5?, urging the discs |57upon the spacer collar i3 and the collar, in turn, against the discvalve |55 to maintain it upon the piston |55. The force exerted by thespring |53 is not sufficient to flex the spring discs |51 so thatnormally the disc valve |55 is urged against the piston |55 at apredetermined pressure and thus it may be said thatdisc valve. is,predeterminately loaded, normally. However, under certain conditions as`will later be explained, fluid. pressure within the -just described.`The Fig. dillustrates, at increased size, the left half of the valvemechanism includingvalvel55. L .1

The upper end surface ofthe piston block |56 is centrally recessed to.provide an annular space |;15 which is constantly in communication withascisse theannular groove |33 .in .piston rod portion |42. `This spaceis in'constant communication with `aniannularV groove |16, inthe uppersurface of the vpiston block, by a series of predeterminately sizedorifices |11 in the block, The outer upper surface .of the piston ischamfered as is the outer lower `surface thereof. The bottom surface ofthe piston block is formed similarly to the upper surface. Thecentralrecess forming annular space y|60 is constantly in communicationwith the annular groove |40 of piston rod portion |42. Metering orifices|8| connect this space |80 with the annular recess |82 in the block.

The piston block |50 has a plurality of ducts which provide for the`transfer of fluid between the working chambers 200 and formed in thecylinder 20 by the piston block. For purposes of this description,chamber 200 will hereinafterA be referred to as the upper-workingchamber and chamber 20|` as the lower working chamber. Every other oneof said fluid ducts 202 in the pist0n block have one end terminating inthe annular groove |16 at the top of the piston, the other endsterminating'in the lower chamfered surface ofthe piston. The other ducts203 have their en'ds terminating respectively in the annular groove |82at `the bottom .of the piston and the chamfered portion of the top sideof the piston. Thus the fluid exit ends of ducts 202 are controlled orrestricted by valve |55 while the entry or bottom ends of said ducts areunrestricted at all times. Likewise, the fluid exit ends of ducts 203are restricted by valve |58 while their top or fluid entrance ends areconstantly free andv open.

.1- .As shown in Fig. l, the tubular piston rod portion |42 has a'ro'd205 of substantially lesser diameter than .the inside diameter ofportion |42 extending coaxially through it, said rod 205 having a headportion .206 secured in the upper end of piston rod portion |42 in anysuitable manner, preferably by welding. This rod 205 is of such a.length that its lower, outer end comes close to the-valve cage 50 whenthe shock absorber is fully collapsed on its compression stroke as shownin Fig. l. i

VThis lower, outer end of rod 205 is threaded to receive nut 201 uponwhich rests the bottom cap 208 of the container |64. A bumper spring 209is supported by said cap 208 which also carries a coil spring 2 |0surrounding rod 205.

An inertia weight 2| centrally apertured to fitloosely around rod 205,rests upon spring 2 l0 and is yieldably supported in normal position bysaid spring. This inertia Weight 2| is within the iiuid filled container|64. A` tubular slide valve 2|5, loosely surrounding Arod 205, has itsone end secured in the inertia weight 2 Il and slidably fits within thepiston rod portion |42. l The inner 4difameterV of the container |64 isgreater than the outer diameter of the inertia Weight 2| so that aspaceV is provided therebetween which is lled with fluid to cushion themovements ofthe weight.- In order toidampen weight movements and renderit insensible of acceleration of f short Ydurationin the movements ofthe piston rod4| upon which Vit isV resiliently supported, yet render itoperative to actuate the slide valve during .accelerated move,- `mentsof the piston rod 4|, of'longer duration, said weight is provided withVa ring 2|2 forming an extending ledge, ftheouter peripheralsurfaceofWhich is closer .to the inner Awall of the con,- tainerV |64 than theouter surface of the weight, thus providing a restriction to the passageof iiuid from one side of the ring 2|2 to the other as the weight movesrelatively tothe container, thereby acting as a dash pot to dampenweight movements. y. t y Two annular grooves 2l6 and 2|1 are providedinthe outer, peripheral surface of the slide valve 2 I5, groove `2I6,when inertia weight 2|| is `in the normal position, connectingtheopenings |46 and |41 inthe piston rod portion |42r and under the sameconditions groove 2|1 connects openings 49 and |50 in saidpiston rodportion. However, under certain accelerated movements of the vpiston |56downwardly, the inertia weight actuates the slide valve to closeopenings |41, and on the other to close `openings |49 inresponse to.predetermined accelerations in the upward movement of the piston |56.. fv i' YThe present shock absorber is .adapted to control the movements oftwo. relatively movable members as forv instance the frame and axle of avehicle. In this case the frame is the sprung mass supported on theaxleby springs which are compressed when the frame Vand axle. move toapproach each otherV and rebounds or expands to separate the frameandaxle and return them to normal position; Thepiston rod portion 40with its attached cap `42 may be-.anchored by any suitable means, tothefframeof the vehicle, and the tube 30 is attachable to the axle ofthe vehicle. Thus as the frame yand axle ofthe vehicle are caused tomove to approach each other, piston |56 will be moved downwardly onwhat-is termed the compression stroke, to exert a pressure upon theiiuid in lower working chamber'20l. When the frame and aXleof thevehicle move to separate due to the action of vehicle springs betweenthe frame and axle,then thef piston |56 is moved upwardly in thecylinder `on what is termed its bound stroke, thereby exerting pressureupon the fluid in the upper working chamber 200.

When ;forinstance, the axle of the Vehicle is thrust upwardly toapproach the frame, and as a consequence the piston |56 is moveddownwardly in cylinder 20 at an acceleration insufficientv to render theinertia control valve 2|5 effective, the piston 56 exerts a pressureupon-the fluid withinthe lower Working cylinder 20|. This fluid pressurewill first be exerted upon the carrier disc 12 and the valve 10supported thereon whereby these elementswill be movedfrom the positionas shown in Fig. 1 into the position as shown in Fig. 2. The valve 10now flexed, still closes the opening in the sleeve valve 60, however,due to its flexing from one position into another, valve 'l0` willactuate` the sleeve valve 60 so that communication is establishedbetween its groove 56 andthe iiuidreservoir 3|.` i Pressure-uponthefluidin the lower working chamber 20| will cause the fluid to flowthrough `piston rod 4| and its piston |56 move at a predeterminedacceleration. The primary control of iiuid flow to cause the shockabsorber to offer resistance to movement is offered bythe valve |55which is normally preloaded by springs |53 and |51. In order that thevalve be lifted from engagement with the piston and thus establish arestricted luid fiow,'meter`ing"orifices y|11 are-'of such a. size as toset up a predetermined back pressure in the annular groove |16 whichwhenit attains a certain value lwill lift valve |55. Fluid will also enterthe interior of the cup shaped piston via the openings |52 in block |5|,however, this fluid in piston |10 is not effective as long as openings|41 are not restricted or closed by the slide valve 2|5. Thus the valve|55 provides for a restricted flow from the lower into the upper chamberto cause the shock absorber to offer its primary resistance toapproaching movements of the two relatively movable members betweenwhich the shock absorber is connected. The fluid displaced from thelower working chamber 20| into the upper working chamber 200 cannotcompletely be received by said upper chamber due to the presence of thepiston rod'in said upper chamber. Therefore, fluid displaced by this rodwill pass through the openings 54 in the cylinder into the space 24thence into the annular groove 53 of the valve cage, through slots 55,space 56, now open, into the reservoir 3 If the downward movement of thepiston is accelerated at a predetermined rate, so that the inertiaweight 2| cannot follow the movement of the piston, then, due to itsinertia, weight 2|| will operate the sleeve valve 2 I5 relatively to thepiston rod portion |42 so that openings |41 will be reduced orsubstantially closed and thereby restricting or actually stopping theiluid flow in the circuit including openings |41 and the annular groove'2|6 of the slide valve 2|5. Now the entire fluid pressure is exertedupon the 'valve |55 and under these circumstances the loading on saidvalve is increased. To do this a portion of the fluid flow is directedthrough orifices |11, space |15, annular groove |33 and openings |52into the interior of the cup-shaped piston |10, said fluid exerting apressure upon said cupshaped piston in addition to the pressure eX-erted thereupon by the spring |53 to urge it into increased pressingengagement with the spring discs |51. The pressure actuated piston |19will now flex the inner portion of spring discs |51 so that, throughthespacer collar or ring |34, the valve |55 is urged toward the piston|55 with an increased force thus valve |55 will oifer its greatestrestriction to uid flow during this accelerated movement of the pistonand the shock absorber its greatest resistance to movement.

When the frame and axle of the Vehicle are moved to separate due to therebounding movement of the vehicle springs, the piston of the shockabsorber is moved upwardly in its cylinder piston |55 starts to moveupwardly, the valve 10 and its carrier 12 will be lifted, resultingfirst in 8 the release and movement of the sleeve Valve 60 into itsnormal position by springs 62 as shown in Fig l where communicationbetween the upper working chamber 200 and the reservoir is discontinuedand at the same time lifting of the valve 10 will open communicationbetween the reservoir 3| and the lower working chamber 20| through saidsleeve valve 60, inasmuch as valve 10 is now disengaged from said sleevevalve and also from its seat 14.

Pressure upon the fluid in the upper working Achamber 200 cannot forcethe uid through openings 54 and annular passage 24 into the reservoir,for'the sleeve valve 60 now closes communication between the upperworking chamber and the reservoir, and as has been mentioned heretofore,sleeve valve 60 is balanced so as not to be effected by fluid pressure.

In response to pressure on the uid in chamber 205, the first iiow occursthrough the following circuit: through the piston passages 203 intoVannular groove |82, thence through metered oriiices ISI in the piston,to the annular groove |48, inthe piston rod portion |42, thence throughopenings |49 in said portion to the annular groove 2|'l' in the slidevalve, thence through the openings |50 in the piston rod portion |43through the passages provided by the annular serrations or corrugationsin the bottom of the disc |62 and thence into the lower working chamber20|. This circuit is the one to be controlled by the inertia valve andthus is designed to normally by-pass the minimum volume of fluid.

The primary controlling ow of fluid is past the valve mechanismincluding valve |58 and spring discs |59. As has previously been stated,this valve mechanism is similar to the Valve mechanism including valve|55 and functions in identical manner. As long as the inertia weightcontrolled sleeve valve 2|5 maintains openings |59 open, valve |58operates under normal preload to control fluid ow from the pistonpassages 203. However, when due to predetermined acceleration in theupward movement of the piston assembly, valve 2|'5 closes openings |49and thus causes full iiuid pressure to be established within thecup-shaped piston |1|, thereby to increase the loading on valve |58,then Valve |58 will increase its restriction and thereby cause the shockabsorber to offer a greater resistance to the separating movements ofthe frame and axle of the vehicle.

From the foregoing it may be seen that applicant has provided ahydraulic, direct acting, inertia controlled shock absorber in which allof the controlling uid flow is directed through the piston of the sho-ckabsorber.

One of the valves in the valve cage at the bottom of the cylinder actsas an intake valve, the other as a valve which either opens and closescommunication between the upper working chamber of the cylinder and thereservoir. Under no circumstances do the valves in the valve cage at thebottom of the cylinder provide for movement controlling, restrictedflows of fluid. As has been said before, all restricted fluid owsproviding for the resistances oifered by the shock absorber to suchmovements are established only through the piston.

While the embodiment of the present invention as herein disclosed,constitutes a preferred form, it is to be understood that other formsmight be adopted, all rcoming within the scope of the claims whichfollow.

What is claimed is as follows:

1. An hydraulic shock'absorber comprising, in combination, a cylinderhaving a valve cage at one end; a piston forming two working chambers insaid cylinder, said piston having a plurality of fluid passagesproviding for the transfer of fluid between said chambers; spring loadedvalves and an inertia weight controlled valve for regulating fluid flowthrough the piston passages as the piston is reciprocated; a fluidcontaining reservoir in communication with both working chambers; andvalves in the valve cage, each normally cutting off communicationbetween a respective working chamber and the reservoir, one of saidvalves opening to permit fluid from the reservoir to enter the onechamber as the piston moves away from the valve cage, said one valveengaging the other valve and being operative by` fluid pressure as thepiston moves toward the valve cage, to actuate said other valve topermit fluid to iiow from the other working chamber into the reservoir.

2. An hydraulic shock absorber comprising, in combination, a cylinderhaving a head at one end and a valve cage at the other; a pistondividing the cylinder into two working chambers, said piston havingpassages connecting the two chambers, one group of said passages havingdual uid flow control means comprising a spring loaded valve and aninertia valve for controlling the fluid flow through said one group ofpassages in one direction, the other group having similar spring loadedand inertia valves for controlling fluid flow through the piston in theopposite direction; a fluid containing reservoir in communication withboth working chambers; and valves in the valve cage each normallyshutting off communication between a respective chamber and thereservoir, one of said valves operating in response to movement of thepiston in one direction, to permit fiuid to flow from the reservoir intothe one chamber and in response to movement of the piston in theopposite direction to actuate the other valve in the cage for permittingthe fluid to'flow fromthe other chamber into the reservoir.

communication between the other chamber and the reservoir. l t

4. An hydraulic shock absorber comprising, in combination, a cylinderhaving a head at one end. and a valve cage at the other; a piston havinga rodslidablyv extending through the head and dividing the cylinder intctwo working chambers and having passages connecting the two chambers;pressure actuated and inertia Weight actuated valves operative, inresponseto movements of the piston in one direction or the other, tocontrol the flow of fluid through said piston passages; Va fluidcontaining reservoir inv communication with both working chambers; andtwo valves in the valve cage each normally ,closing the communicationbetween a respective working chamber and the reservoir, one of saidvalves being balanced as regards pressure effect, the other beingoperative by fluid pressure as the piston moves in one direction to opencommunication between the one working chamber and reservoir to permitIfluid to flow into said chamber and being operative to actuate thebalanced valve to open communication between the other chamber andreservoir as the piston moves in the other direction.

3. An hydraulic shock absorber comprising, in

combination, a cylinder having a head at one end and a valve cage at theother; a piston having a rod slidably extending through thehead anddividing the cylinder into the working chambers and having passagesconnecting the two chambers; dual fluid flow controlling means for onegroup of said piston passages, one of said means normally closing itsportion of said group of passages but operative in response to 'fluidpressure in the one chamber to establish a fluid now into the otherchamber, the other, an inertia weight controlled means normallymaintaining its passage portion open but operative in response topredetermined acceleration in the movement of the piston in onedirection to shut oi the fluid flow through its passage portion, theother group of piston passages having similar fluid pressure and inertiaweight controlled means controlling uid ow similarly, but in theopposite direction and in response to opposite movement of the pist0n; afluid containing reservoir connected to both working chambers; andvalves in the valve cage, each normally'shutting off communicationbetween a respective working chamber and the reservoir, the one valvebeing operative by fluid pressure as the piston moves in one directionto open communication between the one chamber and reservoir, and as thepiston moves in the other direction to actuate the other valve to open5. An hydraulic shock absorber comprising, in combination, a cylinderhaving a head at one end and a valve cage at the other; a piston havinga rod slidably extending through the head and dividing the cylinder intotwo working chambers and havingrpassages connecting the two chambers;pressure actuated and inertia weight actuatedv valves-operative, inresponse to movements of the piston in one direction or the other, tocontrol the flow of fluid through said piston passages; a fluidcontaining reservoir in com-V munication with Iboth working chambers;and two valves-in the valve cage each normally closing the communicationbetween a respective workingchamber and the reservoir, one of saidvalves being balanced as regards pressure effect, the other beingoperative by fluid pressure as the piston moves toward the head of thecylinder to open'communication between the chamber adjacent the valvecage and the reservoir to permit fluid to fiow from said reservoir intosaid chamber and being operative also, as the piston moves toward thevalve cage to actuate the balanced valve and thereby open communicationbetween the reservoir and the chamber adjacent the head member. Y

6. An hydraulic shock absorber comprising, in combination, a l cylinderprovided with a head member at one end and a valve cage at the other; apiston in said cylinder forming two working chambers therein, saidpiston having passages providing communication. between said chambers; arod extending through the head member and attached to the piston; dualmeans for cony trolling the fluid ilow through the piston passages asthe piston is reciprocated in one direction or the other, said meanscomprising a valve on each side of the piston normally providing themaximum restriction to fluid fiow through a respective group of saidpassages and comprising also an inertia weight controlled valve normallyproviding a minimum restriction to said fluid flow but adapted toincrease its restriction in accordance with accelerations in thereciprocating movements of the piston and rod; a fiuid containingreservoir in communication with both working chambers; and valves in thevalve cage, each normally shutting off communication between thereservoir and a respective chamber,

one of these valves permitting uid to flow from the reservoir into onechamber as the piston moves in one direction, the other of these valvesbeing-engaged and moved directly by said one valve, to opencommunication between the other chamber and reservoir as the pistonmoves in the opposite direction.

'7. An hydraulic shock absorber comprising, in combination, a cylinderhaving a head at one end and a valve cage atthe other; a rod extendingthrough the head and having a piston slidable in the cylinder anddividing said cylinder into two chambers; a fluid containing reservoirin ccmmunication with each of said cylinder chambers; a plurality ofducts in the piston providing communication between the two cylinderchambers, certain of said ducts having a two-way discharge outlet intothe one chamber, one normally open and the other normally closed by aresilient spring valve on the piston, the other ducts having asimilartwo-way discharge outlet into the other cylinder chamben'one normallyopenthe other normally closed by a resilient spring valve on the otherside of the piston; an inertia valve resiliently suspended on the pistonrod for controlling the two normally open discharge outlets inaccordance with acceleratio-ns in the reciprocation of the piston rodinone direction or the other respectively; and valves in the valve cage,one, normally shutting off communication between the one cylinderchamber and the reservoir, but adapted to permit fluid to iiowunrestrictedly into said chamber as the piston moves in one direction,the other valve normally shutting oli communication between the otherchamber and the reservoir but operated by the intake valve moved inresponse to the movement of the piston in the opposite direction to opencommunication between said other chamber and the reservoir.

8. An hydraulicsho-ck absorber comprising, in combination, a cylinderprovided with a head member at one end and a valve cage at the other anddivided into two working chambers by a piston having a rod extendingthrough the head member and passages pr'ovidingfor the transfer of fluidbetween said chambers as thel piston is reciprocated; pressure actuatedand inertia weight controlled valves on the piston and in the rod. forcontrolling the flow of fluid between said' chambers as the piston isreciprocated; a fluid containing reservoir in direct communication witheach working chamber; and two Valves in the valve cage, the firstnormally shutting ofi communication between thereservoir and the workingchamber adjacent the valve cage, but operative in response to fluidpressure, as the piston moves away from the valve cage, to open andpermit Huid ow from the reservoir into the last mentioned chamber, thesecond valve being balanced against the eiTects of fluid pressure andnormally cutting off communication between the chamber adjacent the headmember and the reservoir, but being operative directly by the said rstvalve as the piston moves toward the valve cage, to

open communication between the chamber containing the piston rod and thereservo-ir to permit fluid displaced by said piston rod to flow into thereservoir. A

9. An hydraulic shock absorber comprising, in combination, a cylinderprovided with a head, member at one end and a valve cage at the otherand vdivided into two working chambers by a piston having a rodextending through the head member and passages providing for thetransfer f fluid between said chambers as the pSQl ,is

chambers as the piston is reciprocated; a iuidi containing reservoir indirect communication. with each working chamber; and two valves in the-xvalve cage, the first normally shutting off communication between thereservoir and the working chamber adjacent the valve cage, but opera--tive in response to iiuid pressure, as the pistonmoves away fromtheivalve cage, to open and permit iiuid ow from the reservoir into thelast mentioned chamber, the second Valve being balanced againstthe-effects of iiuid pressure and normally, yieldably'urged into contactwith the said rst Valve for cutting oi communication between the chambercontaining thepiston rod and the reservoir and being operative by thesaid first valve in the cage as the piston moves toward said valve cage,to open communication between the chamber containing the piston rod andthe reser-l voir to permit uid displaced by said rod to ilow to thereservoir.

l0. An hydraulic shock absorber comprising in;

combination, a cylinder having a head member at, one end and a valvecage at `the other, a piston dividing said cylinder into two workingchambers, said piston having passages connecting said two chambers; aresilient disc valve at each end of' the piston, each valve controllingthe flow of fluidi from a respective group'of said passages as thepiston is reciprocated; a normally open fluid'. shunting circuit in thepiston leading from each: group of passages around the valve into thedisplacement chamber into which the respective passages discharge whensaid valves open; a valve; loading mechanism for each disc valve, saidmechanism constantly being in communication with theshunting circuit; aninertia weight controlled' valve having means normally forcing oneportion of the shunting circuit but operative in response topredetermined accelerative movements of the piston to close the shuntingcircuit. whereby the loading mechanism is energized to exert anincreased pressure upon the valve to increase its restriction to fluidflow; a uid containing reservoir in communication with both workingchambers; and valves in the valve cage each normally shutting oficommunication between the respective chamber and the reservoir, one ofsaid valves operating in response to movement of the piston in onedirection, to permit fluid to flow from the reservoir into the onechamber and in response to movement of the piston in the oppositedirection to actuate the other valve in the cage for permitting thefluid to flow from the other chamber into the reservoir.

l1. An hydraulic shock absorber comprising in combination, a cylinderhaving a head member at one end and a valve cage at the other; a pistondividing the cylinder into two working chambers, said piston having aplurality of fluid passages connecting said two chambers; a resilientdisc Valve engaging each end of the piston, each valve controlling theow of fluid through a respective group of said passages, one in onedirection, the other valve in the opposite direction; normally openfluid passages provided by the piston, each leading from beneath arespective valve to the working chamber into which said valve is adaptedto discharge iluid; a valve loading mechanism comprising a block carriedby the piston and a cup-shaped member slidably fitting about said block,forming a space between it and the blot-k in ,constant communicationwith said normally containing reservoir in communication with bothWorking chambers; and valves in the valve cage each normally shuttingofi communication between a respective chamber and the reservoir, one ofsaid valves operating in response to movement of the piston in onedirection, to permit fluid to ow from the reservoir into the one chamberand in response to movement of the piston in the opposite direction toactuate the other valve in the cage for permitting the uid to flow fromthe other chamber into the reservoir.

EDWIN F. ROSSMAN.

